Abstract
Various invasive ant species have negatively affected reproductive success in birds by disrupting nest site selection, incubation patterns, food supply, and by direct predation on nestlings. Impacts can be particularly severe when non-native ants colonize seabird nesting islands where thousands of birds may nest in high densities on the ground or in burrows or crevices. Here we report on the first documented effects of Myrmica rubra, the European fire ant, on the reproduction of birds in its non-native range. We documented herring gulls (Larus argentatus) on Appledore Island, Maine, engaging in more erratic incubation behaviors at nests infested by the ants. Newly-hatched chicks in some nests were swarmed by ants, leading to rapid chick death. Due to high overall rates of chick mortality, survival probabilities did not vary between nests with and without ant activity, however chick growth rates were slower at nests with ants than at ant-free nests. Ant infestation likely leads to longer-term fitness consequences because slower growth rates early in life may ultimately lead to lower post-fledging survival probabilities.
Highlights
The effects of invasive organisms on native species are of growing concern as globalization leads to the translocation of species and biotic homogenization [1,2]
Incubation observations were conducted for 1260 minutes at 35 herring gull nests (20 with ant activity)
Birds incubating at nests with ant activity engaged in more preening and other behaviors disrupting incubation than birds at nests without ant activity (Table 1, x21 = 17.49, p,0.001)
Summary
The effects of invasive organisms on native species are of growing concern as globalization leads to the translocation of species and biotic homogenization [1,2]. Island-nesting birds may be vulnerable to population decline due to the limited availability of suitable nesting islands and the potential development of super-colonies of non-native ants following invasion [5,6]. Birds are able to establish a nest but are disturbed by ant activity during the incubation period. This can result in metabolic costs to the incubating adults and reduced incubation efficiency [9]. Numerous studies document the effects of invasive ants on newlyhatched chicks, when birds are most vulnerable and swarming by ants can lead to chick death or nest abandonment by adults [5,10,11,12]. Even in the absence of direct chick morality attributed to ant activity, ants at the nest can negatively affect chick growth rates, potentially compromising the long-term survival of the chick [13]
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